BRAINSAVER: Development of a novel cardiopulmonary resuscitation feedback device using carotid doppler ultrasound

Georg Maximilian Stachel (Leipzig)1, R. Fuchs (Leipzig)2, N. Sumrah (Leipzig)1, M. Schultz (Merseburg)3, R. Klaua (Merseburg)3, T. Neumuth (Leipzig)2, U. Laufs (Leipzig)1, K. Lenk (Leipzig)1

1Universitätsklinikum Leipzig Klinik und Poliklinik für Kardiologie Leipzig, Deutschland; 2Innovation Center Computer Assisted Surgery Leipzig, Deutschland; 3Gesellschaft für Angewandte Medizinische Physik und Technik Merseburg, Deutschland


Introduction: Survival after out-of-hospital cardiac arrest (OHCA) is still dismal. Feedback devices to ensure high-quality chest compression might improve outcomes. We set out to develop a novel feedback device using carotid ultrasound. Our aim is a device which can be deployed rapidly and reliably by non-ultrasound-trained medical personnel, and which gives clear feedback concerning the quality of chest compression.

Methods and Results: We used a specifically developed and compactly build ultrasound probe employing three ultrasonic elements in order to account for the unknown angle of doppler ultrasound insonation (patent pending, Fig. 1 A, denoted by asterisk). The probe uses pulsed-wave (pw) doppler ultrasound. To place the probe reliably, we constructed a mounting using a Stifneck extrication collar (Laerdal Medical, Copenhagen, Denmark, Fig 1 A and B). The probe can be slid along the mounting on a rail, covering different positions (Fig 1 A, denoted by arrow).     

We evaluated the power score defined as the transformation of the entire determined blood flow curve into the image/frequency range by the discrete Fourier transformation, in which the powers of the periodic parts of the flow curve are determined and plotted as a function of frequency as a parameter of signal quality at 5 different positions denoted as millimeter (mm) positions along the rail in the mediolateral direction in each subject and at 7 different depths between 3.75 – 27.75 (mm) of the pw doppler window. We tested the probe and the collar on n=25 volunteers. Data are presented median (interquartile range p0,25 – p0,75).

Anthropometric baseline characteristics are height 185 (169 – 189) cm, weight 73 (63 – 79) kg, BMI 22.25 (21.45 – 23.13) kg/m², neck circumference 37 (34.0 – 38.5) cm, neck length 19.5 (17.0 – 21.5) cm.  The evaluation yielded interpretable doppler spectra between positions 35 mm and 95 mm in the mediolateral direction in most of the subjects (Pos. 55 mm: 86.4% of subjects, 65 mm: 63.6 % of subjects, 75 mm: 54.5 % of subjects as the most successful positions). Power scores of these positions were 2.01 (1.30 – 2.20) (55 mm), 2.05(1.79 – 2.34) (65 mm) and 2.05 (1.86 – 2.21) (75 mm). Fig. 2 shows an exemplary doppler spectrum indicating an analyzable signal.

Conclusion: The first in-human evaluation of our novel ultrasound-based feedback device yielded promising results showing quick deployment and reliability of measurement in a first cohort of volunteers. The data set the stage for further evaluation in healthy volunteers before testing in patients with critical cardiocirculatory state and under cardiopulmonary resuscitation. 

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